Diane Curtis and Ellen Leuchs tied the knot in May 2004, less than a week after Massachusetts legalized same-sex marriage and a decade after beginning their life as a couple.

To the U.S. Census Bureau, however, their marriage does not count. Or, more specifically, it will not be counted in the 2010 census.

Although gay marriage is legal in Massachusetts and California, census officials say that same-sex partners in both states who list themselves as spouses will be recorded as "unmarried partners" -- just as they were in the 2000 census.

Census Bureau spokesman Stephen Buckner cited the Defense of Marriage Act, approved by Congress and signed by President Bill Clinton in 1996, which prohibits the federal government from recognizing as a marriage the union of anyone but a man and a woman.

The law "requires all federal agencies to recognize only opposite-sex marriages for the purposes of administering federal programs," Buckner wrote in an e-mailed statement. "Many of these programs rely on Census Bureau statistics."

Census officials have said the agency will retain same-sex spouses' original responses but will edit them for the published census tabulations. The policy was first reported by the San Jose Mercury News.

Curtis, 45, of Sunderland, Mass., said she was "disgusted."

"The effect is just to erase our marriages and our families, really," said Curtis, a lawyer who has two children with Leuchs, 40, a fundraiser.

Critics of the policy -- and the law -- say it ignores the changing legal and political landscape in states that contain about 14 percent of the U.S. population. And it ensures that the census results will be factually incorrect, they say.

"Unfortunately the stupidity and unfairness of that law gives [the census] something of a colorable argument," said Rep. Barney Frank (D-Mass.). "It was aimed very specifically at this. It's all the more reason to repeal it. . . . What is it accomplishing by not having an accurate count? It's not even good demographic policy."

The lack of data about same-sex married couples will inhibit researchers who want to better understand a variety of issues, such as wage differences for gay married couples and discrimination on the basis of sexual orientation, said Gary Gates, a demographer at the UCLA School of Law.

"It limits our ability to get quality information," said Gates, author of the Gay and Lesbian Atlas. "In 2000, the census could very legitimately make the argument that with a same-sex couple, someone couldn't [legally] be a husband or wife. And so they were making an inaccurate response accurate by changing them to an 'unmarried partner.' The situation now is different. You are changing potentially accurate responses to inaccurate responses."

The policy will, for example, require that the couple's children be listed as having single parents, Gates said. And it will cause the census to undercount families, defined as two or more people in the same household related by birth, adoption or marriage, he said.

In Massachusetts, 10,490 same-sex couples were married between May 2004 and August 2007, according to state figures. California, which began same-sex marriages last month, does not keep similar figures. A ballot initiative would amend the state Constitution to ban same-sex marriage.

Peter Sprigg, vice president for policy at the nonprofit Family Research Council, argued that the Census Bureau's policy makes sense both demographically and legally. He said his group will "vigorously defend" the Defense of Marriage Act if critics try to overturn it.

"We believe that marriage is intrinsically the union of a man and a woman," Sprigg said. "The reason marriage is a public institution in the first place is that it brings together men and women for the reproduction of the human race and to encourage mothers and fathers to cooperate in raising to maturity the children produced by their union."

Curtis likened the Census Bureau's stance to something out of the Cold War era.

"It's like we've been Photoshopped out of the picture," she said. "How long is the federal government going to pretend we don't exist?"